Various methods to record on a recording carrier, such as paper or plastic film, typically Mylar, Reg. .TM. for oriented polyester film are known; in one such method, a recording carrier is used which has a substrate of paper or Mylar, (Reg. .TM.) which is metalized. The substrate is moved beneath a writing electrode, for example a plurality of comb-like projections which engage closely adjacent spots on the carrier and which are selectively energized as the carrier is moved beneath the comb-like array of the electrodes by a transport mechanism, for example a roller or the like. As current pulses are applied to the respective selected electrodes, the metal cover on the substrate is removed, leaving the substrate exposed. To provide for good legibility, it has been proposed to coat the substrate with a lacquer or ink which can be applied, for example, by a printing method. Record carriers which are to be looked at from the top usually have a substrate which is opaque, for example paper; if the recording on the record paper is to be read by transmission, the substrate is usually transparent, for example a transparent plastic film of Mylar.
The electrical pulses applied to the comb-electrode array burn off a pattern of points or lines from the surface of the substrate recording carrier in order to provide a corresponding image of the original, for example by generating a predetermined dot configuration or line configuration, as the carrier is moved perpendicularly with respect to the lateral extent of the comb-electrode array.
The recording carriers are usually in the form of sheets or tapes. The electrosensitive coating thereon may be zinc, aluminum, or a zinc-cadmium alloy, and applied on the electrically insulating substrate in a vacuum by vapor deposition. The pattern to be reproduced is burned in by the respectively energized writing electrodes positioned, for example, in a straight line across which the substrate carrier is pulled. The respective comb electrodes are appropriately energized from an electical energy source in accordance with the scanning signals which are to reproduce the image. The contrast of the visible output and the corrosion resistance of the recording medium can be improved, as known, by placing a black layer of ink or lacquer beneath the electrosensitive coating in order to permit ready reading of the image which is reproduced.
For recordings which are to be read by transmission of light therethrough, for example in which the light is applied towards the recording carrier from the side of the substrate, or if the recording carrier is to carry information which is to be photographically reproduced, it is desirable to not only make the recording carrier transparent, but also to utilize a transparent lacquer when applying the layer of the lacquer on the substrate. It has also been proposed to utilize a substrate which is uniformly colored, but transparent, for example which is tinted with a color which is particularly appropriate for subsequent copying on paper especially sensitive to the tint color.
The recording methods and the record carriers as known permit reproduction only of black-white images and, to some extent, of intermediate grey tones. The black-content of the intermediate grey tones can be obtained by suitable subdivision of the image to be reproduced into finely adjacent points, or to adjust the size of the burned-out points at any particular location, in order to obtain a grey-tone image similar to the dot pattern used in half-tone image representation in printing methods.